SILGen: Fix calls to literal constructors defined in protocol extensions

Fixes <https://bugs.swift.org/browse/SR-3173>.

Author: slavapestov

lib/SILGen/SILGenApply.cpp

@@ -4694,15 +4694,16 @@ static RValue emitApplyAllocatingInitializer(SILGenFunction &SGF,
   {
     // Determine the self metatype type.
     CanSILFunctionType substFnType =
-      SGF.getLoweredType(substFormalType, /*uncurryLevel=*/1)
-      .castTo<SILFunctionType>();
+      initConstant.SILFnType->substGenericArgs(SGF.SGM.M, subs);
     SILType selfParamMetaTy = substFnType->getSelfParameter().getSILType();
 
     if (overriddenSelfType) {
       // If the 'self' type has been overridden, form a metatype to the
       // overriding 'Self' type.
       Type overriddenSelfMetaType =
-        MetatypeType::get(overriddenSelfType, SGF.getASTContext());
+        MetatypeType::get(overriddenSelfType,
+                          selfParamMetaTy.castTo<MetatypeType>()
+                              ->getRepresentation());
       selfMetaTy =
         SGF.getLoweredType(overriddenSelfMetaType->getCanonicalType());
     } else {

validation-test/compiler_crashers_2_fixed/0061-sr3173.swift

@@ -0,0 +1,31 @@
+// RUN: %target-swift-frontend %s -emit-silgen
+
+protocol P: Equatable, ExpressibleByStringLiteral {
+    var uid: String { get }
+    init(uid: String)
+}
+
+extension P {
+    // Equatable
+    public static func ==(lhs: Self, rhs: Self) -> Bool {
+        return lhs.uid == rhs.uid
+    }
+
+    // ExpressibleByStringLiteral
+    public init(stringLiteral value: String) {
+        self.init(uid: value)
+    }
+    public init(unicodeScalarLiteral value: String) {
+        self.init(uid: value)
+    }
+    public init(extendedGraphemeClusterLiteral value: String) {
+        self.init(uid: value)
+    }
+}
+
+struct Test: P {
+    var uid: String
+    static let s1: Test = "s1"
+}
+
+Test.s1 == "test"